1. Field of the Invention
This invention relates generally to the field of virtual display systems. More particularly, the invention relates to a system and method for scanning a virtual image on a retina.
2. Description of the Related Art
Traditional display systems such as television and computer monitors produce xe2x80x9crealxe2x80x9d images. This means that the light waves producing the image actually emanate from the image point. Thus, as illustrated in FIG. 1, a traditional monitor such as a cathode ray tube (xe2x80x9cCRTxe2x80x9d) produces an actual image 110 by irradiating pixels on a monitor 120 using an electron beam. Light waves emanating from the image 110 are then focused by the cornea (not shown) and the focused image is reproduced on the retina 140 (i.e., the back surface of the eye).
There are several problems with real image display systems. For example, these systems are typically large and cumbersome and require substantial amounts of power to operate (e.g., to illuminate the individual pixels on the CRT). In addition, these systems to not provide an adequate level of privacy. Anyone within the visual range of a CRT monitor 120 is able to view its contents, making these systems ill-suited for viewing confidential material in public places (e.g., on an airplane).
To solve some of these problems xe2x80x9cvirtualxe2x80x9d display systems were developed. In contrast to a xe2x80x9crealxe2x80x9d display system, a xe2x80x9cvirtualxe2x80x9d display system is one in which the light producing the image does not actually emanate from the imagexe2x80x94it only appears to.
One type of virtual display system scans photons which contain image data directly onto the retina of a user""s eye. As illustrated in FIG. 2, a photon source 220 such as a laser diode generates a coherent beam of light (the photon source 220 may actually be three photon sources if a color image is rendered). The beam of light is intensity-modulated by modulation unit 230 to match the intensity of the image being generated. A beam scanner 240 receives the modulated signal and scans the modulated signal across the retina using a particular scan pattern (e.g., raster scan pattern, vector scan pattern . . . etc). An optical projection unit 250 may be comprised of one or more lenses for properly focusing the scanned pattern into the eye.
Although the virtual display system illustrated in FIG. 2 solves some of the problems associated with real display systems (described above), a number of problems remain. Most of these problems stem from the fact that both the beam scanning unit 240 and the optical projection unit 250 must be located in close proximity to the user""s eye (i.e., so that the scanned signal may be properly positioned to scan across the user""s retina). Accordingly, to implement the system of FIG. 2, a user must wear a headset or a pair of virtual display glasses which include a substantial amount of hardware.
One obvious problem with this configuration is that it forces a user to wear a heavy, bulky apparatus which may dissipate a substantial amount of heat. While such a system may be acceptable for specialized purposes (e.g., an army helicopter helmet, medical surgery glasses . . . etc) it is unlikely that mainstream users are willing to wear such a device on a regular basis.
Accordingly, what is needed is a virtual display system and method which solves the foregoing problems.
A virtual image system is disclosed comprising: a passive optical unit for interfacing with portions of a user""s head; and an optical projection unit directing a retinal scanning beam into the passive optical unit, the optical projection unit detached from the passive optical unit.